This invention relates generally to outdoor units for air conditioners/heat pumps and, more particularly, to a method and apparatus for adapting the orifice to reduce sound levels and flow losses.
Air cooled condensers, as commonly used in residential air conditioning systems, employ fin tube construction to transfer heat from the refrigerant to the outdoor air. As hot, high pressure refrigerant passes through the coil, heat from the compressed refrigerant is transferred through the tubes to the attached fins. An electrically powered fan is then used to draw large quantities of outside air across the fin heat transfer surfaces to remove heat from the refrigerant so that is will condensed and partially subcooled prior to its reaching the expansion valve.
In heat pump application, the same outdoor unit operates in much the same manner but the heat exchanger operates as an evaporator rather than a condenser. Air conditioners and heat pumps are sometime referred to generically as comfort systems.
The heat exchanger coil of an outdoor unit is usually round, rectangular, or square in form, and the compressor is normally disposed within the coil. A fan and its drive motor is commonly mounted above the heat exchanger coil such that the fan draws outdoor air inwardly through the coil and then upwardly to be discharged into the atmosphere.
In order to guide the airflow stream in the vicinity of the fan, i.e. particularly as it flows radially inwardly to the fan and as it is discharged to the atmosphere at the top of the fan, a so called orifice structure is included at the top of an outdoor unit to provide a smooth surface over which the air is caused to flow. Typically the orifice has a cross section that resembles an inverted U with an outer leg wrapped over the outer side of the coil and an inner leg which extends downwardly in the vicinity of the fan. At the lower end of the inner leg, there is a slight radially outward flare, but the inner leg normally protrudes into the airflow stream.
The applicants have recognized that the inner leg or orifice leading edge causes flow disturbances, thereby resulting in efficiency losses and increased sound levels. Ideally, the outwardly flaring portion of the inner leg would be extended to provide a smooth surface over which the air can flow rather than a sharp edge that disrupts the flow pattern. However, the normal process of forming the orifice structure from sheet metal does not allow such an approach because of splitting or tearing of the sheet metal material that tends to occur.